Protected pages have "edit" text instead of "view source" on the action=edit link.
Clicking the link does get a source view page instead of an edit page.
Protected pages also display edit links on sections, unlike 1.4, but I see that
as a feature.
Tested locally with all shipped enabled skins, and as anonymous editor.
No proxies are used.
Tried refreshes, forced-refreshes, restarting server processes, action=purge,
and emptying cache table.

(In reply to comment #1)
> Also in 1.5, the "Older revision" and "Newer revision" links are missing from
> source view pages of old revisions.
> Hopefully this has the same cause.
Nope, that feature isn't in 1.4 either, so I'll report a separate request.